Total Soil Volume Research Articles

Vertical Distribution of Soil Removed by Four Species of Burrowing Rodents in Disturbed and Undisturbed Soils

Burrow volumes were determined in disturbed and undisturbed soils for four species of rodents in southeastern Idaho. Comparisons were made between soil types for the average volume and the proportion of the total volume of soil excavated from 10-cm increments for each species, and the relative number of burrows and proportion of total soil removed from beneath the minimum thickness of soil covers over buried low-level radioactive wastes. Burrows of montane voles (Microtus montanus) and deer mice (Peromyscus maniculatus) rarely extended below 50 cm and neither volumes nor depths were influenced by soil disturbance. Townsend's ground squirrels (Spermophilus townsendii) had the deepest and most voluminous burrows that, along with Ord's kangaroo rat (Dipodomys ordii) burrows, were more prevalent beneath 50 cm in disturbed soils.

Accumulation and partitioning of dry matter and mineral nutrients in developing kiwifruit vines.

Size, dry weight and mineral nutrient content of fruit, leaves, shoots, canes, leader, stem and roots of kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson var. deliciosa) vines, aged from one to five years, were measured. The distribution of fruit yield among single canes was examined in three of the vines. Total dry weight increased from a mean of 1.29 kg vine(-1) for one-year-old vines to 29.2 kg vine(-1) for five-year-old vines. The proportion of total dry weight in roots declined from the first to the third year (55 to 40%) and then remained approximately constant, whereas the proportion of dry weight in fruits increased from the first to the third year before attaining a more or less constant value. The proportion of total canopy dry weight contained in the current season's growth (fruit, leaves and shoots) averaged 75% for all ages. Roots of five-year-old vines had only penetrated a small proportion of the total soil volume available. Total fruit yield increased linearly with number of floral shoots for whole vines and single canes within vines, but with cane size (length or dry weight) for whole vines only. The productivity of single canes declined from 2.5 kg m(-1) for canes shorter than 0.25 m to about 1.1 kg m(-1) for canes longer than 1.0 m, in accordance with a declining bud density with increasing cane length. For vines of all ages, mineral nutrient concentrations in various tissues were similar, except that Ca in leaves and S in leaves and shoots increased with vine age. Major sites of accumulation of N, Ca, Mg, S, Fe, Mn and B were the leaves, whereas P and K accumulated predominantly in the fruits, Zn in the leader, and Na and Cu in the roots. Estimated annual mineral nutrient uptake increased with vine size and fruit yield, and for five-year-old vines the values per hectare were 141 kg N, 19 kg P, 169 kg K, 161 kg Ca, 28 kg Mg, 32 kg S, and less than 2 kg for Na and all micronutrients. The nutrient content of the harvested fruit provided an inaccurate estimate of annual nutrient uptake of the developing vines.

THE EFFECT OF ANHYDROUS AMMONIA APPLICATIONS ON THE SOLUBILITY OF SOIL ORGANIC CARBON

The rapid increase in anhydrous ammonia use in Western Canada has created concerns about possible detrimental soil effects, particularly solubilization of organic matter. Anhydrous ammonia was injected at rates of 0.206, 0.416 and 0.834 g NH3-N into undisturbed soils taken in 20-cm-diameter cylinders. Both field capacity (FC) and permanent wilting point (PWP) moisture contents were used. Samples were taken at 0–2.5, 2.5–5.0, 5.0–7.5 and 7.5–10.0 cm from the injection point, 1 day after injection. For the 0.416 g NH3-N rate samples were also obtained 35 days after injection. Soluble organic carbon (SOC) was measured in a 1:15 soil:water extract. The SOC was closely related to the NH4+-N concentration (r2 = 0.79 to 0.99; P < 0.001). The SOC was increased by NH3 at all injection rates for samples within 2.5 cm of injection point, at the highest rate for the 2.5- to 5.0-cm zone but there were few effects in the 5.0- to 7.5-cm zone and none in the 7.5- to 10.0-cm zone. The solubilized C was 0.3–4.6%, 0.0–3.0% and 0.0–0.6% of the total C in the 0- to 2.5–cm, 2.5- to 5.0-cm and 5.0- to 7.5-cm zones, respectively. The 0- to 2.5-cm, 2.5- to 5.0-cm and 5.0- to 7.5-cm zones represent 4.3, 13.1 and 21.8%, respectively, of the total soil volume. Thus carbon solubilized is insignificant when expressed on a total soil basis. Key words: Anhydrous ammonia, soil organic C, soluble organic C, soil deterioration

Soil‐plant Diversity Relationships on a Disturbed Site in Northwestern Colorado

AbstractA 5‐yr‐old revegetation plot in the Piceance Basin of northwestern Colorado was used to study the relationship between several soil properties and plant species diversity. Soil properties, including coarse fragment content, topography, depth to bedrock, rooting depth, soil volume, fertility, and salt content, were quantified for 108 subplots. Using simple and multiple regression techniques, plant diversity on the subplots was correlated with the various soil properties. A seed mixture composed of introduced grasses and forbs was used most extensively to study diversity‐soil physical property relationships. For these plots, percent large coarse fragments (> 4.76 mm) within the rooting depth had a high positive correlation with the Shannon‐Weiner diversity index. Depth to bedrock, rooting depth, total soil volume, soil volume within the rooting depth, and a topographic index all exhibited negative correlations with the Shannon‐Weiner index. On plots seeded with a native grass‐forb seed mixture, where variation in salt content was greatest, SAR, ESP, and EC had positive correlations with species richness. When all seed mixtures were considered, rate of fertilizer application had a negative correlation with the Shannon‐Weiner index. In every case where a regression was significant, soil properties normally associated with high production resulted in low diversity and soil properties normally associated with low production resulted in high diversity. Mechanisms are proposed to explain the relationships between soil factors and diversity. Management techniques are also suggested which could be incorporated into the reclamation process to increase plant diversity.

Plant Accumulation and Soil Sorption of Cobalt from Cobalt‐Amended Soils1

AbstractPresent industrial uses of Co result in elevated metal concentrations in soils around industrial activities and land treatment facilities. Laboratory and greenhouse studies were conducted to determine Co uptake by tall fescue (Festuca arundinaceaSchreb.) as affected by soils, Co levels, lime additions, Mn additions, and soil layering. In a laboratory sorption study using solutions containing 5 to 1000 mg Co L−1, the Marietta (Aquentic Dystrochrepts) and Norwood (Typic Udifluvent) soils had sorption maxima of 1440 and 3787 mg Co kg−1, respectively. The higher sorption of the Norwood soil was presumably due to the formation of complexes or precipitates between the CaCO3and Co. Addition of up to 6.7 Mg lime ha−1resulted in decreased concentrations of Co in tall fescue grown in soils containing 400 mg Co kg−1. Addition of 50 to 2000 mg MnO2kg−1soil had no effect on Co accumulation by tall fescue. Layering of uncontaminated soil over Co‐amended soil increased plant uptake of Co over that taken up by plants grown in Co‐amended soil alone. Apparently, the healthy roots in the upper layers of soil removed Co from the lower layers of soil; whereas, elevated Co in the total soil volume retarded root development sufficiently to prevent Co uptake. Total Co determinations were as good as or better than any of the three extractants (2.5% acetic acid, 0.01 MEDTA [ethylenediamine tetracetic acid] and DTPA‐TEA [diethylenetriamine pentacetic acidtriethanolamine]) in predicting plant accumulation of Co. Of the tested extractants, acetic acid had the lowest correlation coefficient when compared with plant Co accumulation.

Sorghum root growth and water-use as affected by water supply and growth duration

Early (‘58M’) and late (‘90M’) isogenic lines of sorghum (Sorghum bicolor L. Moench) were grown in a root observation field installation at Temple, Texas in 1976, in order to study the effect of soil moisture and growth duration on root development and plant water-use. The installation consisted of soil-filled steel chambers equipped with a glass panel and installed in retaining structures in the ground. Each chamber was lifted out of the ground for weighing and measuring roots visible on the glass panel. In all chambers, soil was irrigated to field capacity prior to planting. Two soil moisture regimes were then imposed — an irrigated treatment, wherein irrigation was applied whenever soil moisture content was reduced to 50% of available soil water; and a stress treatment, wherein no irrigation was applied and plants grew on stored soil moisture. Transpiration was considerably less for the early than for the late genotype in relation to the respective leaf area of the two genotypes. Transpiration demand was met without apparent plant stress, as long as the soil moisture content of the total soil volume was greater than 20% of available soil water. Below 20% of available soil water, transpiration was controlled mainly by a reduction in leaf area through leaf senescence. Total cumulative root length per plant and root length density were larger and root length density per unit leaf area was smaller for the late than for the early genotype. Root length density per unit of green leaf area increased under conditions of soil moisture stress due mainly to the reduction in green leaf area. Root distribution along the soil profile was highly skewed (higher root concentration at shallow than at deep soil layers) with irrigation and more homogeneous without irrigation. Root growth at shallow soil layers was promoted by irrigation. Root mortality of approximately two-thirds of the total cumulative root length produced by heading was recorded. Root mortality was not only associated with total plant senescence, but with plant age and rooting depth.

Influences stationnelles sur l'alteration chimique des sols derives de till (Sherbrooke, Que., Canada)

In a small watershed of the canadian Appalachians, five trenches were studied in two catenas facing each other, one forested, the other under recent prairie vegetation (100 years of age), to investigate the character of chemical weathering in these sites. On the top of the forested catena there was a humo-ferric fragic podzol, and further down, and orthic gleysol. The other catena had a humo-ferric fragic podzol, then, downwards, a grey gleyified luvisol and a luvic fragic gleysol. Percolating waters near these trenches were sampled regularly, at various depth. The distribution of the ions on the meadow side indicated on one hand that H 4SiO 4, Na + and Mg 2+ in percolating waters are related to the total volume of soil through wich waters percolate, that the dissolution of aluminium is accelerated in acid sites (upslope) and that the solubility of iron reaches a maximum in the zone influenced by the water table. On the other hand, calcium, which is easily liberated in the high sections, is in part fixed when the solutions get concentrated, iron and aluminium are soon traped, silicium is less mobile than the basic cations. The constituants of primary minerals organize as follows: concentration of Al 2O 3 and Fe 2O 3 upslope, when the contrary is for the basic oxydes and SiO 2; this trend stands out more clearly in the top 30 cm. Thus on top of the forested catena, chemical weathering is intense, the aluminium and iron oxydes are highly evacuated in this podzol. At the same altitude, in the prairie podzol, which probaly had 100 years ago a less acidifying vegetation (hardwoods) than in the first case, feldspars and micas are degraded and we find mostly transformed minerals (montmorillonite — Al). Minerals are very much less degraded downslope because of their confined position and the high ionic content of the percolating waters.

PHOSPHORUS NUTRITION OF SOYBEANS AS AFFECTED BY PLACEMENT OF FERTILIZER PHOSPHORUS

Growth chamber and field experiments were conducted on Southern Manitoba soils, low in available soil phosphorus, to investigate the effects of various placement methods and levels of phosphorus fertilizer on soybean (Glycine max (L.) Merrill ’Maple Presto’). It was found that soybean responded well to applied phosphorus on low-P soil in growth chamber studies. In the first growth chamber experiment, P was applied in solution to 100%, 50%, 25%, 12.5% and 1% of the total soil volume. Dry matter yields, total phosphorus uptake and utilization of fertilizer P increased at each level of applied P as the size of the phosphated band was decreased. The results were partly attributed to greater chemical availability of P in the smaller zones of P fertilizer reaction. In a second growth chamber experiment, soybeans responded differently to phosphorus banded in six different locations. Placement of the fertilizer 2.5 cm directly below the seed was more effective in increasing dry matter yield, total phosphorus uptake and fertilizer P utilization than placement 2.5 cm and 5 cm away at the same depth or placement 5 cm below the seed, whether the band was directly below, 2.5 cm away or 5 cm away. Soybean yield responses in the field were greatest with P banded 2.5 cm directly below the seed on low-P soils. Placement of P 2.5 cm below the seed resulted in grain yields that were 64% and 50% higher (at the two sites) than those obtained in control plots. Sidebanding P, 2.5 cm below and 2.5 cm away from the seed at the same level of application, improved grain yields of control plots by 40% and 39%. Seed placement and broadcast applications of P were not as effective in increasing grain yields. Broadcasting P in fall or in spring at rates of up to 52.38 kg P/ha did not result in significantly higher grain yields than those obtained in control plots. Placement of P in contact with the seed appeared to reduce seedling emergence, resulting in depressed yields when 52.38 kg P/ha were applied. Key words: Glycine max L. Merrill, ’Maple Presto’

Influences stationnelles sur l'alteration chimique des sols derives de till (Sherbrooke, Que., Canada)

In a small watershed of the canadian Appalachians, five trenches were studied in two catenas facing each other, one forested, the other under recent prairie vegetation (100 years of age), to investigate the character of chemical weathering in these sites. On the top of the forested catena there was a humo-ferric fragic podzol, and further down, and orthic gleysol. The other catena had a humo-ferric fragic podzol, then, downwards, a grey gleyified luvisol and a luvic fragic gleysol. Percolating waters near these trenches were sampled regularly, at various depth. The distribution of the ions on the meadow side indicated on one hand that H 4 SiO 4 , Na + and Mg 2+ in percolating waters are related to the total volume of soil through wich waters percolate, that the dissolution of aluminium is accelerated in acid sites (upslope) and that the solubility of iron reaches a maximum in the zone influenced by the water table. On the other hand, calcium, which is easily liberated in the high sections, is in part fixed when the solutions get concentrated, iron and aluminium are soon traped, silicium is less mobile than the basic cations. The constituants of primary minerals organize as follows: concentration of Al 2 O 3 and Fe 2 O 3 upslope, when the contrary is for the basic oxydes and SiO 2 ; this trend stands out more clearly in the top 30 cm. Thus on top of the forested catena, chemical weathering is intense, the aluminium and iron oxydes are highly evacuated in this podzol. At the same altitude, in the prairie podzol, which probaly had 100 years ago a less acidifying vegetation (hardwoods) than in the first case, feldspars and micas are degraded and we find mostly transformed minerals (montmorillonite — Al). Minerals are very much less degraded downslope because of their confined position and the high ionic content of the percolating waters. Dans un petit bassin-versant des Appalaches canadiennes, cinq fosses pédologiques ont été étudiées dans deux caténas de part et d'autre de l'exutoire, l'une sous forêt, l'autre sous prairie récente (la déforestation datant de 100 ans), afin de caractériser l'altération dans divers sites le long de la pente. La première caténa comportait, de haut en bas du versant, un podzol humo-ferrique fragique, un luvisol gris gleyifié, un gleysol luvique fragique; la deuxième, sous forêt, un podzol humo-ferrique fragique, un gleysol orthique. Les eaux de percolation de ces profils ont été prélevées régulièrement, à diverses profondeurs ainsi que l'eau de l'exutoire. La distribution des ions dans la caténa sous prairie a indiqué que d'une part les teneurs en H 4 SiO 4 , Na + et Mg 2+ sont liées au volume traversé, que l'aluminium est plus fortement mis en solution dans les sites acides (hauts de versants), que les teneurs en fer sont maximales dans les niveaux influencés par le battement de la nappe phréatique. D'autre part, le calcium, fortement libéré sur les hauteurs, se fixe en partie lorsque les solutions se concentrent, le fer et l'aluminium sont piégés très tôt alors que le silicium est moins mobile que les cations basiques. Les constitutants des minéraux primaires dans les sols s'organisent donc ainsi: concentration de Al 2 O 3 et Fe 2 O 3 vers le haut de versant, alors que c'est le contraire pour les oxydes basiques et SiO 2 , ce qui est plus évident dans les 30 cm de surface. Aussi, en haut de versant de conifères l'altération est intense, les sesquioxydes sont fortement évacués dans ce podzol, tandis qu'à la même hauteur dans le podzol de prairie, qui portait il y a 100 ans sans doute une végétation moins acidifiante (feuillus) que dans le premier, la dégradation (des minéraux phylliteux et des feldspaths) et les transformations (en montmorillonite — Al) prédominent. La dégradation des minéraux est faible dans les bas de versants par suite du confinement et de l'élévation des teneurs des percolats.

The Mechanism of Raindrop Splash on Soil Surfaces

AbstractFrom the results of high‐speed photography of 4.6‐mm‐diam drops impacting various soil materials and from soil mechanics principles, a new concept in describing the mechanism of soil detachment from raindrops impacting on saturated soil surfaces is proposed. The impulsive loading caused by the impacting drop does not permit time for drainage; thus there is no change in total soil volume or bulk density. The soil surface is deformed under the impulsive load application of the drop; however, the vertical strain under the impact area is compensated by a bulge around the perimeter of the depression. The vertical force of the drop is transformed to lateral shear caused by radial flow of the impacting drop. Splash angle is determined by the depth of the cavity and the size of the bulge surrounding it.Splash angle was highly correlated with soil shear strength as measured by the fall‐cone method. Low soil strength resulted in (i) a larger cavity and surrounding bulge, (ii) a greater detachment of soil particles due to the shear stress of the radial flow, and (iii) a greater splash angle with the horizon.

Phosphorus Application Rate and Distribution in the Soil and Phosphorus Uptake by Corn

AbstractEvaluation of the effect of P addition and distribution in soil on P uptake by corn (Zea mays L.) plants, requires knowledge of the relation of soil P level to corn root growth rate and morphology. This research was conducted to obtain these relationships so that they could be used with root P influx and soil supply characteristics to calculate P uptake. Corn was grown for 12 and 18 days on two soils, each with five levels of P application, in pots in a controlled climate chamber. Root growth and P uptake were measured. Except for the lowest rate, increased rate of P mixed uniformly with the soil decreased average root length per pot even though shoot growth increased. Placing a common rate of P per pot in part of the soil volume increased root growth in the P‐treated soil volume as compared to root growth in the untreated soil. The difference was expressed by the relation y = x0.68, where y was the fraction of total plant root length in x, the fraction of the total soil volume that was P treated. Separate calculation of P uptake from each soil volume showed low P uptake from the untreated soil compared to that from the treated soil. Predicted P uptake per not calculated with a mathematical simulation model was correlated (r = 0.81 and 0.78 for the two soils) with observed P uptake. Information on effect of P on corn root growth and on P influx can be used in mathematical models to investigate relative P uptake from alternate P application practices.

Mechanical limitations to successful amelioration of soil structure — Demonstrated on a deep ploughed loess parabraunerde (Udalf)

The results of deep ploughing of a parabraunerde derived from loess (Udalf) are discussed. Changes in soil water characteristics and total soil volume and the vertical stress situation in the soil profile before and after deep ploughing are compared with a similar, but non-tilled, forest soil. Deep ploughing makes the structure of the orchard soil only temporarily more or less similar to that of the non-tilled forest soil. Conclusions are drawn concerning the conditions under which the loosening due to deep ploughing might be conserved.

Phosphorus Response of Corn on an Oxisol as Influenced by Rates and Placement

AbstractPhosphorus deficiency and high P sorbing capacities are a major limitation to intensive cropping of many soils in the Cerrado area of Central Brazil. A field study comparing rates and placement of P for corn (Zea may L.) was conducted to determine initial and long‐term P fertilization requirements. Rates of broadcast P were 70, 140, 280, and 560 kg P/ha and banded rates were 35, 70, and 140 kg P/ha. In addition, combination treatments of 140 or 35 kg P/ha broadcast and banded rates of 35 kg/ha per crop were used.Broadcast treatments gave greater yields than band treatments at the same rates for the first crop. At the end of four crops, however, total yields and P uptake were very similar for broadcast and band treatments in which the same total amount of P had been applied. Marked residual effects were observed with the higher rates of broadcast P.A greenhouse study was conducted in which a given amount of P was mixed with varying proportions of the total soil volume. Corn growth and P uptake were a function of both the concentration of P in the portion of the soil fertilized and the percent of the total soil volume that was fertilized. These results tend to explain the increase with time in relative yields of the banded treatments.The best method for applying P to these high adsorbing soils appears to be an initial broadcast application of 140 kg P/ha and a band application of 35 kg P/ha to each crop. This treatment maintained the available soil P at the critical soil test level and produced 80 to 85% of the maximum yield.

PHYSICAL PROPERTIES OF GLEYSOLIC SOILS IN THE LOWLANDS OF QUEBEC

Clay-rich soils were sampled in the agricultural areas of Montreal, Quebec and Lake St-Jean. Undisrupted soil blocks and bulk samples were taken by horizon in the Ste-Rosalie, Kamouraska and Normandin soil series. Aggregate stability increased with the organic matter content. Bulk density was generally highest in the B horizons. Porosity ranged from 39 to 56% of the total soil volume and the most representative pore diameter varied from 0.706 to 0.048 μm with the largest diameter being found in the Ap horizons. The distribution of porosity among large, medium and small pores in the Ste-Rosalie soil differed from that in the Kamouraska and Normandin soils. In the former, medium pores accounted for only a few percent of total porosity, while the pores were more evenly distributed in the latter soils. Medium pore contents decreased, while small pore contents increased, with increasing clay contents. No significant relationship was observed between large pores and clay percentages. Hydraulic conductivity, with mean values ranging from 3.5 to 109.3 cm/h, was significantly related to the large pore class.

Effects of Soil Temperature and Soil Moisture in Podding Zone on Pod Development of Peanut Plants

To examine the effects of soil temperature and soil moisture in the podding zone on the pod development of a peanut variety, Chiba-handachi (large seed, semi-erect type), three experiments were carried out under the condition separating the podding zone from that in which the roots were grown. In experiment-I in 1969, the mean soil temperatures in the podding zone were 38.6°C, 30.6°C, 22.9°C and 15.3°C. Experiment-II was performed under four soil moisture conditions, namely 57.3, 40.3, 21.5 and 7.8 percent to the total soil volume. In experiment-III, the effects of the treatments combining high soil temperature (37-39°C) and low soil moisture (6-8 percent) in the podding zone in every 10 days after the peg penetration upon the pod development were exermined. The results obtained were as follows. 1. The beginning time and the rate. of the pod development were affected remarkably by soil temperature in the podding zone. The following relations were observed between the pod development and soil temperature in the podding zone. Optimum soil temperature ; 31 to 33°C Minimum soil temperature; 15 to 17°C Maximum soil temperature; 37 to 39°C 2. It was recognized that the optimum soil moisture content in the podding zone was about 40% to the total soil volume, regardless of the soil moisture content in the rooting zone. When the soil moisture content was lower than 40%, the podding percentage and the thickening growth of the pod were reduced, and when it was higher than 40%, only the thickening growth of the pod was reduced. 3. Considering the rsults obtained in experiment-III, the most critical period in the pod stage was the first 30 days, especially between 20 to 30 days after the peg penetrated into the soil.

Canfield Silt Loam, a Fragiudalf: II. Micromorphology, Physical, and Chemical Properties

AbstractAlthough cutans comprise less than 1 to 2% of the total soil volume, they impart a disproportionately large influence to the soil as a medium for plant growth. This impact is maximized in the Canfield fragipan where rooting volumes are almost exclusively restricted to polygonal ped interfaces. Sampling these morphological units of fragipan horizons revealed twice as much total clay and three times as much < 0.2µ clay in the cutan segments of the horizon as in the matrix material or bulk horizon sample. Quantities of exchangeable cations were roughly proportional to the clay content, but the exchangeable K and Sr were nearly four and five times more concentrated, respectively, in the cutanic material, suggesting a possible mineralogical difference between the cutan and matrix or bulk mineralogy. X‐ray analysis indicated that the total clay fraction of the cutan material contained a greater proportion of nonexpandable and expandable 14Å and 17Å minerals, as well as interstratified components, when compared to the matrix and bulk clay fraction. Thin section analysis in conjunction with textural analysis and profile descriptions verified the presence of an argillic horizon above the fragipan and revealed the laminar morphology of the polygonal interface. From these data and observations the genetic sequence of the Canfield series is suggested.

Nutrient Utilization by Young Pitch Pine

AbstractTen pitch pines (Pinus rigida Mill.) ranging in age from 5 to 9 years were excavated from an abandoned gravel pit in southern New Jersey. Lateral and vertical distribution of the root systems were recorded and total soil volume occupied by roots was calculated (root system sorption zone). In addition, the volume of soil within 1 cm. of any root surface was calculated (root surface sorption zone). Contents of total and exchangeable Ca and K in these zones were related to contents of Ca and K in the trees. Exchangeable Ca and K contents in the root system sorption zone were generally higher than the total content of these nutrients in the trees while the reverse was true for the relationship between the root surface sorption zone and the tree. Annual uptake of K by the trees was approximately equal to exchangeable K content of the root surface sorption zone. Annual uptake of Ca by trees was only about one‐third of the exchangeable Ca in the root surface sorption zone indicating that average distance of movement of Ca from soil to root surface was less than that for K. Less than 10% of the total soil volume occupied by roots was utilized in absorption of Ca and K.

Estimation of Particle‐Size Effects of Water‐Soluble Phosphate Fertilizer in Various Soils

AbstractA laboratory method was developed for estimating the relative availabilities to plants of the P applied to soil in fertilizer particles differing in size. The method is based on the concept that the total availability of fertilizer P applied in particles of a given size is equal to the product of (a) the number of particles of that size, and (b) the summation of the availabilities of fertilizer P in the hypothetical small volumes of soil that may be considered to comprise the total volume of soil affected by a single particle. The method was applied experimentally to NaH2PO4·H2O particles of three sizes in each of six soils. In this application, appropriate quantities of a concentrated solution of P32‐tagged NaH2PO4 were used to stimulate the effects of fertilizer particles of different sizes, and particles of anion‐exchange resin were used to provide indexes of availability of fertilizer P in segments of the soil affected by one fertilizer particle. These values were integrated to obtain an index of total availability of fertilizer P. The indexes of total availability obtained from the laboratory data were in qualitative agreement with the relative availabilities of fertilizer P to plants in five of the six soils tested.

Some Soil Factors Influencing the Density of Cereal Root Eelworm (Heterodera Avenae Woll.) Populations and Their Damage To the Oat Crop

In a survey of 32 oat fields infested with Heterodera avenae Woll. the soil factors affecting the success of the crop at various levels of eelworm density were examined. Of these, water holding capacity was found to be the most important, and after that the phosphorus status. Potassium and organic matter had little effect until they were very low, and pH had no noticeable affect. The proportion of the total soil volume with pore spaces between 30 and 100 μ in diameter was calculated for each soil and named the Available Pore Space (APS). Low figures for this appeared to have a limiting effect on the build up of cysts when many cereal crops were grown.

Row widths and inter-row cultivation of potatoes

Investigations were started in 1957 by the National Institute of Agricultural Engineering into possible ways of simplifying the problem of the mechanical harvesting of potatoes by suitable cultivation techniques. “Bed” cultivation was tried in which 2, 3 or 4 rows were grouped together leaving a wide track for tractor and implement wheels. This method of growing potatoes was finally rejected as the yield of crop was adversely affected due to overcrowding in the middle rows of the “beds”. It was found that at least 550 square inches were required by each plant in the “bed”, and at this spacing many of the advantages of “bed” cultivation were lost. Difficulty was also experienced in covering the potatoes and preventing greening. Later work with 36 inch rows showed that the crop was not adversly affected by the wide rows in comparison to the conventional 28 inch row. but in an experiment on a heavy wet soil there was twice the amount of clod in these wide rows, due apparently to the greater total volume of soil and the inaccessibility of much of it to cultivation. Rotary inter-row cultivation using an experimental machine consisting of three pairs of contra-rotating spiders gave a third of the amount of clod as that of a set of lister bottoms (taken to represent mouldboard ridging). Present work is being concentrated on rotary inter-row work using a prototype commercial machine, and indications are that rotary interrow work in potatoes can be very effective in breaking up clods and giving a fine tilth in the ridge.